Synchrotron x-ray study of a low roughness and high efficiency K2CsSb photocathode during film growth

Junqi Xie, Marcel Demarteau, Robert Wagner, Susanne Schubert, Mengjia Gaowei, Klaus Attenkofer, John Walsh, John Smedley, Jared Wong, Jun Feng, Howard Padmore, Miguel Ruiz-Oses, Zihao Ding, Xue Liang, Erik Muller, Ilan Ben-Zvi

Research output: Contribution to journalArticlepeer-review

18 Scopus citations

Abstract

Reduction of roughness to the nm level is critical of achieving the ultimate performance from photocathodes used in high gradient fields. The thrust of this paper is to explore the evolution of roughness during sequential growth, and to show that deposition of multilayer structures consisting of very thin reacted layers results in an nm level smooth photocathode. Synchrotron x-ray methods were applied to study the multi-step growth process of a high efficiency K2CsSb photocathode. A transition point of the Sb film grown on Si was observed at the film thickness of ∼40 Å with the substrate temperature at 100 °C and the growth rate at 0.1 Å s-1. The final K2CsSb photocathode exhibits a thickness of around five times that of the total deposited Sb film regardless of how the Sb film was grown. The film surface roughening process occurs first at the step when K diffuses into the crystalline Sb. The photocathode obtained from the multi-step growth exhibits roughness in an order of magnitude lower than the normal sequential process. X-ray diffraction measurements show that the material goes through two structural changes of the crystalline phase during formation, from crystalline Sb to K3Sb and finally to K2CsSb.

Original languageEnglish
Article number205303
JournalJournal of Physics D: Applied Physics
Volume50
Issue number20
DOIs
StatePublished - Apr 24 2017
Externally publishedYes

Funding

Work at Argonne National Laboratory was supported by the U S Department of Energy, Office of Science, Office of Basic Energy Sciences and Office of High Energy Physics under contract DE-AC02-06CH11357. Work at BNL, LBNL and Stony Brook University was supported by the US DOE, under contracts DE-AC02-05CH11231, DE-AC02-98CH10886, KC0407-ALSJNT-I0013, and DE-SC0005713. Use of the National Synchrotron Light Source, Brookhaven National Laboratory, was supported by the U S Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-98CH10886. Use of CHESS was supported by the NSF and NIH/NIGMS via NSF award DMR-1332208.

Keywords

  • bialkali antimonide photocathode
  • critical angle
  • grazing incidence small angle x-ray scattering
  • roughness
  • thickness
  • x-ray diffraction
  • x-ray reflectivity

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